1. Field of the Invention
The present invention relates to a network monitoring and controlling apparatus that collects quality information in a transmission network.
2. Description of the Related Art
In the case of a transmission network such as an SDH (Synchronous Digital Hierarchy) network, a SONET (Synchronous Optical network) or the like, frame data inputted from a low-speed line of a terminal or the like is outputted through a high-speed line to a low-speed line. An input channel of a transmission apparatus where the frame data is inputted from the low-speed line to the transmission network is referred to as an entrance point; an output channel of a transmission apparatus where the frame data is outputted to the low-speed line is referred to as an exit point; and input and output channels of transmission apparatus relaying the frame data are referred to as path via points. A logical communication path connecting the entrance point with the exit point and extending over a plurality of transmission apparatus is referred to as a path.
The points on the path are set as cross connect information in the corresponding transmission apparatus. The transmission network has a redundant structure such as a ring structure or the like from a viewpoint of improving reliability. For each path, an active path and a reserve path are set. The active path refers to a path through which frame data outputted by the transmission apparatus at the output point passes. The reserve path refers to a path that has an intermediate path different from that of the active path and through which frame data not outputted by the transmission apparatus at the output point passes. A network monitoring and controlling apparatus is provided to collect quality information in the transmission network and change over from the active path to the reserve path.
Conventionally, an operator instructs the network monitoring and controlling apparatus to collect quality information of each active path, and determines whether there is quality deterioration. When there is quality deterioration, the operator determines whether to change over to the reserve path. The operator then instructs the network monitoring and controlling apparatus to change over to the reserve path.
However, the conventional network monitoring and controlling apparatus has the following problems.
(1) As described above, the operator refers to quality information, determines whether to change over, and performs the changeover for each path. Hence, there is a fear of the operator being late in noticing quality deterioration. If the operator is late in noticing quality deterioration, there is a high possibility of an interruption of communication before switching the path, which is very hazardous for network management.
(2) Even when the operator recognizes the quality deterioration of an active path, the operator needs to collect information again in order to grasp a state of quality of a reserve path, and thus takes time to determine whether changeover to the reserve path is necessary.
(3) Known examples of monitoring line quality and changing over from an active path to a reserve path depending on the state of quality include Japanese Patent Laid-Open No. Hei 7-321882 “METHOD AND DEVICE FOR MONITORING LINE IN MODEM NETWORK WITH MONITORING FUNCTION,” Japanese Patent Laid-Open No. 2000-83036 “METHOD AND DEVICE FOR CONTROLLING DATA TRANSFER,” Japanese Patent Laid-Open No. 2000-151607 “IP PACKET COMMUNICATION DEVICE AND OPTICAL NETWORK,” and the like. All these examples only monitor quality of the active path and change over to the reserve path depending on a result of monitoring the quality of the active path. Since the examples do not monitor quality of the reserve path, even when the line quality of the reserve path is lower than the line quality of the active path, the changeover is performed without knowing that the line quality of the reserve path is lower than the line quality of the active path.
(4) Further, for each path, quality information of input and output points of transmission apparatus for forming paths of the path is collected. Therefore a load on the network is increased. In order to avoid the problem by reducing the load, it is necessary to collect quality information of only the input and output points of the path. However, a problem of trade-off is presented, in that at a time of occurrence of quality deterioration, in order to identify a point causing the quality deterioration, the operator needs to collect quality information of input points of all the transmission apparatus on the path, and is thus late in determining whether to perform changeover.